The best framework is the one you would have built yourself, but which is improved and promptly bugfixed by someone else. :)

I still disagree. Frameworks are usually multipurpose general 'jack of all trades master on none' type things. Unless you've built your own based on some specific use case(s).

It's extremely unlikely that it'll be improved by someone else in exactly the direction you need it to be improved based on your particular use case.

Depends how important it is to your success though.

... except where you have new employees who need to use it, and you don't have any documentation. This is, to me, the one of the best parts about using Django or Rails--the ramp up time for new hires is lessened by being able to hire experienced developers in "framework X" from the get go, or when hiring juniors one can simply point them at a tutorial.